Bumped die and other bumped devices are widely used throughout the electronics industry. As the drive toward smaller electronics continues, the pitch (or spacing) of the conductive bumps on bumped devices continues to decrease. The increasingly finer pitches of the conductive bumps raise concerns about the reliability of these devices, placing greater emphasis on the accuracy and efficiency of bumped device testing.
FIG. 1 is an isometric view of a conventional conductive bump array contactor 10 that may be used to test a bumped device 20 (commonly referred to as a Device Under Test or DUT) having an array of conductive bumps 22. The bumped device 20 includes a substrate layer 24 and an encapsulating layer 26. The array contactor 10 includes a base 12 having a plurality of cylindrical apertures 14 disposed therethrough. A spring probe 16 is disposed within each aperture 14, each spring probe having a first end 15 and a second end 17. The first end 15 may be flush with, or extend slightly from, a top opening 18 of the aperture 14. Similarly, the second end 17 may be flush with, or extend slightly from, a bottom opening 19 of the aperture 14. Conductive bump array contactors 10 of the type shown in FIG. 1 are described in U.S. Pat. No. 5,5780,033 to Staab.
During testing, the bumped device is positioned over the base 12 with the conductive bumps 22 aligned with the openings 18. The bumped device 20 engages the base 12 so that each of the conductive bumps 22 is in contact with the first end 15 of one of the spring probes 16. The bumped device 20 may be pressed against the base 12 so that the first ends 15 are at least partially compressed into the spring probes 16. The second ends 19 may then engage a plurality of contact pads of a test machine (not shown), which transmits test signals through one or more of the spring probes 16 to the bumped device 20. The test machine may also receive output signals from the bumped device 20 to determine whether the bumped device 20 is performing according to specifications. After testing, the bumped device 20 may be disengaged from the conductive bump array contactor 10, and another bumped device may be tested in the same manner.
Although desirable results have been achieved using the conductive bump array contactor 10, problems may be encountered during separation of the bumped device 20 from the array contactor 10. For example, while the conductive bumps 22 are in contact with the first ends 15 of the spring probes 16, material from the conductive bumps 22 may migrate and become attached to the first ends 15. This may cause the conductive bumps 22 to become stuck to the first ends 15 of the spring probes 16. When one or more of the conductive bumps 22 becomes stuck to the spring probes 16, the testing process may be delayed as additional time and effort is expended to disengage the bumped device 20 from the array contactor 10.
The sticking or bonding of the conductive bumps 22 to the spring probes 16 occurs with increasing frequency as the number of tests using the array contactor 10 increases. Also, as the number of conductive bumps 22 on the bumped device 20 increases, the probability that more of the conductive bumps 22 will become stuck increases, further decreasing the speed and efficiency of the testing process.
An additional concern with the array contactor 10 is that the bumped device 20 may not be accurately aligned with the top openings 18 of the apertures 14. If the conductive bumps 22 are not precisely aligned with the top openings 18, the first ends 15 of the spring probes 16 may not properly contact the conductive bumps 22, and the testing may provide inaccurate or unreliable results. As the pitch of the conductive bumps 22 decreases, the task of aligning the conductive bumps 22 with the spring probes 16 becomes more difficult.